Shampoos are deliberately formulated to have an extremely high viscosity. This permits one to dispense the shampoo by pouring it from a bottle or squeezing it from a dispenser onto a hand. It is then spread throughout the hair. When combined with water, foam is generated. Shampoos typically have a high viscosity such as the shampoo disclosed in U.S. Pat. No. 4,364,837, which is preferably 400 to 6,000 CPS and most preferably 500 or 1,000 CPS. Robbins et al. U.S. Pat. No. 4,731,201, discloses a shampoo having a viscosity in the range of 500 to 5,000 CPS and Bushman U.S. Pat. No. 4,321,156 discloses a shampoo having a viscosity of 5,000 to 10,000 CPS.
The high viscosity or thickness is believed to be required to provide an acceptable shampoo. However, this viscosity does present certain problems. The higher viscosity interferes with distributing the shampoo evenly across the scalp. Also, being thick, it may be more difficult to apply. The viscosity also limits the method used to dispense the shampoo. A viscous shampoo requires more water as it is applied. This might be very disadvantageous in certain applications.
The viscosity of a shampoo can be easily modified by simply diluting the shampoo. Thin shampoos have significant disadvantages. If a large amount of a very thin shampoo is applied to the scalp, it will run off the scalp before being lathered. Also, if a thinned down shampoo is used, a relatively large container is required.
There are spray applicators used to apply shampoo to a scalp. These are disclosed, for example, in Neale et al., U.S. Pat. Nos. 3,701,475 and 3,752,399, in Charitar et al. U.S. Pat. No. 5,116,253. A wig washing machine is also disclosed in Duncan U.S. Pat. No. 3,828,588. Although there is no disclosure of the shampoo composition dispensed with these applicators, it is generally assumed that a thinned down shampoo would be applied using these applicators.